Pesticides Detected in Bees, Flowers, Soil, and Air within Pollinator-Attractive Row-Crop Border Plantings
Bees are Critical for Food Crop Pollination
USGS studies sources of pesticide exposure for bees and other pollinators
Field study in California describes the potential for pollinator-attractive field borders in agricultural areas to become a pesticide exposure pathway to bees through soil, air, and plants.
Native bees and honey bees (Apis mellifera) are critical for food crop pollination in agroecosystems, yet their populations are declining worldwide. Studies have indicated that some of the bee declines may be related to factors such as substantial loss of habitat and exposure to environmental contaminants, including pesticides used during crop production.
Pollinator-attractive field border plantings (for example, hedgerows and forb strips) are commonly used to promote bee conservation and have been shown to increase bee diversity and abundance in agricultural areas. However, there is a data gap in the science, concerning if plants may contain pesticides from use on adjacent crops and unintentionally result in pesticide exposure for native bees in these plantings.
Understanding the pathways of bee exposure to pesticides (for example, from border plantings, soils where ground bees nest, and the air [drift]) is important in order to design future best management practices that maximize crop production while maintaining protection to bees and other pollinators.
The U.S. Geological Survey and University of California-Berkley scientists completed a study to fill this data gap and better understand pathways for pesticide exposure for different groups of bees in an agricultural landscape. As part of this study, they examined pesticides in native bees, honey bees, flowers, soil, and air (via passive samplers) at field sites on eight farms in an intensively managed agricultural landscape in Yolo and Colusa Counties, California.
Their findings indicate there are several potential pathways of exposure for bees in agriculture landscapes including the air, flowers, and soils that the bees are exposed to during their daily search for food and nesting. A wide variety of pesticides (8 insecticides, 13 herbicides, 12 fungicides, and 4 degradates) were detected in bees, plants, soil, and air. The five pesticides detected most frequently across all samples were the insecticide bifenthrin; the herbicides thiobencarb, metolaclor, and propanil; and the fungicide fluopyram.
The factors contributing to pesticide exposure for bees in agricultural landscapes are complex. Scientists determined that pollinator-attractive field border plants contained pesticides despite pesticides never having been directly applied. Given the detections of pesticides in the soil and air, it is possible the pesticides in the border plants originated from aerial drift and (or) uptake from the soil. In addition to being exposed to pesticides while foraging, bees can encounter pesticides during most activities that they engage in during flight (via aerial sprays or the dust from planting of treated seeds), while walking or resting on the surface of plants and soils, during nesting (in soil, leaves, resins, wax, and other materials), and while feeding.
The pesticide bifenthrin was detected in bee bodies at levels associated with potential sublethal effects in honey bees. Because little is known about how exposure to mixtures of pesticides can change the toxicity of individual pesticides, studies that analyze only a subset of pesticides (for example, neonicotinoids alone) and a subset of bee species (emphasis on honey bees) may not be broad enough to understand if there are larger ecological consequences.
Although this study generated important insights for pesticide exposure to bees in an intensively managed agricultural landscape, much remains to be learned about the frequency of exposure, toxicity of pesticides to native bees and honey bees foraging in agricultural landscapes, and the factors driving differences in pesticide concentrations in bees (metabolism and (or) detoxification), which may lead to lower concentrations in some species. Studies to understand how a number of traits are relevant to pesticide exposure for bees, including sociality, fecundity, nest type (for example, substrate, materials, and period), flower preferences, adult and larval food, body size, and other anatomical and physiological characteristics (for example, how pollen is transported and metabolism), would provide detailed information useful for consideration of future mitigation steps.
This study was supported by the U.S. Department of Agriculture Natural Resources Conservation Service (CIG-69-3A75-12-253 to The Xerces Society), the U.S. Geological Survey Environmental Health Program, and by a University of California Berkeley Connect Fellowship and a University of California Agriculture and Natural Resources Cooperative Extension Graduate Fellowship.
Select feature articles related to pollinators are listed below.
Improving forage for pollinators on Federal conservation lands
Pesticide Exposure to Native Bees in Agricultural Landscapes
Native Bees are Exposed to Neonicotinoids and Other Pesticides
Field study in California describes the potential for pollinator-attractive field borders in agricultural areas to become a pesticide exposure pathway to bees through soil, air, and plants.
Native bees and honey bees (Apis mellifera) are critical for food crop pollination in agroecosystems, yet their populations are declining worldwide. Studies have indicated that some of the bee declines may be related to factors such as substantial loss of habitat and exposure to environmental contaminants, including pesticides used during crop production.
Pollinator-attractive field border plantings (for example, hedgerows and forb strips) are commonly used to promote bee conservation and have been shown to increase bee diversity and abundance in agricultural areas. However, there is a data gap in the science, concerning if plants may contain pesticides from use on adjacent crops and unintentionally result in pesticide exposure for native bees in these plantings.
Understanding the pathways of bee exposure to pesticides (for example, from border plantings, soils where ground bees nest, and the air [drift]) is important in order to design future best management practices that maximize crop production while maintaining protection to bees and other pollinators.
The U.S. Geological Survey and University of California-Berkley scientists completed a study to fill this data gap and better understand pathways for pesticide exposure for different groups of bees in an agricultural landscape. As part of this study, they examined pesticides in native bees, honey bees, flowers, soil, and air (via passive samplers) at field sites on eight farms in an intensively managed agricultural landscape in Yolo and Colusa Counties, California.
Their findings indicate there are several potential pathways of exposure for bees in agriculture landscapes including the air, flowers, and soils that the bees are exposed to during their daily search for food and nesting. A wide variety of pesticides (8 insecticides, 13 herbicides, 12 fungicides, and 4 degradates) were detected in bees, plants, soil, and air. The five pesticides detected most frequently across all samples were the insecticide bifenthrin; the herbicides thiobencarb, metolaclor, and propanil; and the fungicide fluopyram.
The factors contributing to pesticide exposure for bees in agricultural landscapes are complex. Scientists determined that pollinator-attractive field border plants contained pesticides despite pesticides never having been directly applied. Given the detections of pesticides in the soil and air, it is possible the pesticides in the border plants originated from aerial drift and (or) uptake from the soil. In addition to being exposed to pesticides while foraging, bees can encounter pesticides during most activities that they engage in during flight (via aerial sprays or the dust from planting of treated seeds), while walking or resting on the surface of plants and soils, during nesting (in soil, leaves, resins, wax, and other materials), and while feeding.
The pesticide bifenthrin was detected in bee bodies at levels associated with potential sublethal effects in honey bees. Because little is known about how exposure to mixtures of pesticides can change the toxicity of individual pesticides, studies that analyze only a subset of pesticides (for example, neonicotinoids alone) and a subset of bee species (emphasis on honey bees) may not be broad enough to understand if there are larger ecological consequences.
Although this study generated important insights for pesticide exposure to bees in an intensively managed agricultural landscape, much remains to be learned about the frequency of exposure, toxicity of pesticides to native bees and honey bees foraging in agricultural landscapes, and the factors driving differences in pesticide concentrations in bees (metabolism and (or) detoxification), which may lead to lower concentrations in some species. Studies to understand how a number of traits are relevant to pesticide exposure for bees, including sociality, fecundity, nest type (for example, substrate, materials, and period), flower preferences, adult and larval food, body size, and other anatomical and physiological characteristics (for example, how pollen is transported and metabolism), would provide detailed information useful for consideration of future mitigation steps.
This study was supported by the U.S. Department of Agriculture Natural Resources Conservation Service (CIG-69-3A75-12-253 to The Xerces Society), the U.S. Geological Survey Environmental Health Program, and by a University of California Berkeley Connect Fellowship and a University of California Agriculture and Natural Resources Cooperative Extension Graduate Fellowship.
Select feature articles related to pollinators are listed below.